Acoustic transformer



Oct. 8, 1929. P. A. ROBBINS ACOUSTIC TRANSFORMER Filed Nov. 30, 1928.Znlen/Zz I I PQfiZZim /m Patented Oct. 8, 1929* I UNITED STATES PATENT.OFFICE PERCY A. nonam's, onnronrann ranx, ILLINOIS ACOUETIC TRANSFORMERApialicatlon fled November 30, 1928. Serial No. 522,899.

I disclosed a closed cham' er containing a gaseous medium havingagreater powertransmitting capacit pheric, pressure in w ich chamber istotally immersed a vibratable diaphragm from which or to whichvibrations pass solely through the gaseous medium a) orfrom a seconddiaphragm exposed-at one side to the 7 atmosphere and at the other sidesure within the chamber.

My object in the presefit invention is to provide a simple form of theinvention which is cheaply and easily made, and which gives a maximumarea to the second diaphragm obtainable within given over all dimensionsof the apparatus.

\ I attain my object by reducing the rigid part of the chamber to suchdimensions as sufiice only for the connection and support of the parts,and by utilizing, to complete to the presthe chamber and form thediaphragm, a substantially spherical shell formed of a lickible elasticmaterial such as thin rubber.

The invention is hereinafter more specifically described and illustratedin the accompanyin drawing which is a vertical section of the evice. y

. Referring to the drawing, 1 is a diaphragm operated by theelectro-magnet 22. The diaphragm is held in place by the ring 4. and thewhole is mounted on the cup 3. This is a usual type of loud speaker unitand I, make no claim thereto as any suitable type may be used. I

The cup 3 is screwedonto a tube 6, which is screwed into a connectingnipple 7 which is screwed onto a stand tube 8 screwed into the V base 9.Electricconductors 55 connect'the magnet 22 with the connecting bolts18-18 Y which on their outer ends are connected to electric conductors19-19 which supply, the current for operating the diaphragm 1.

15 is a circular disk of wood or other nonconductor of electricityforming the base of the gas chamber of the device. 16 is a rubberballoon similar to those used for toys but than air at atmos-" having asomewhat larger neck opening. The balloon neck is stretched over thediaphragm and cup 3, and is then stretched over the disk 15 to engage ina peripheral groove around I the latter. A binding string or elastic 17holds the balloon neck tightly in place making a gas tight joint.

10 is a branch tube fitted into the tube. 8 and having the valve seat 12and the valve 11 mounted internally. 13 is a spring for holding thevalvedn place. I make no claim for novelty in the construction of tube10 and the valve, and any arran ement similar to an automobile tirevalve wi I serve the purpose. 14 is the usual cap for closing the end oftube 10. r

I wish to surround the diaphragm with a heavy dense gas, and one way toaccomplish this is to use the carbon dioxide of the human breath.Respired air is blown in through the tube 10. The tube 8 is packed withany porous absorbent for removing moisture from the stream of air. Thedensity of the air in the balloon 16 may be regulated by the pressure ofinflation. If greater pressure is reuired, more respired air isblown inthrough t e tube 10. If decreased pressure is required, some of the aircan be released by pushing on the stem of the valve 11.

202O are holes in the tube 6 for allowing the air to flow into theinterior of the balloon. The upper end of the tube 6 communicateswiththe interior of the cup 3 so that the cup is filled with gas underpressure and the diaphragm 1 is in contact with the same pressure anddensity of gas on both of its sides.

Apparatus constructed as described will satisfactorily attain theobjects of my invention as set forth in the specigcation.

What I claim as my invention is:

1; An acoustic transformer comprising a base; a substantially sphericalthin shell connected withthe base and forming therewith a gas tightchamber; means for admitting a gaseous medium under pressure into saidchamber; and a vibratahle diaphragm immersed in said gaseous medium andentirely enclosed by said chamber.

2. An acoustic transformer comprising a base; a substantially sphericalshell of elastic material connected with the base and forming therewitha gas tight chamber; means for admitting a gaseous medium under pressureinto said chamber; and a vibratable diaphragm immersed insaid gaseousmedium entirely enclosed by said chamber.

3. An acoustic transformer comprising a base; a substantially sphericalthin shell connected with the base and forming therewith a gas tightchamber; means for admitting a gaseous medium under pressure into saidchamber extending through said base; and a vibratable diaphragm immersedin said gaseous medium entirely enclosed by said chamber.

4. An acoustic transformer comprising a base; a substantially sphericalshell of elastic material connected with the base and forming therewitha gas tight chamber; means for admitting a gaseous medium under pressureinto said chamber extending through said base; and a vibratablediaphragm imanersed in said gaseous medium entirely enclosed by saidchamber.

Signed at Highland Park, 111., this 15th day of November, 1928.

PERCY A. ROBBINS.

